Wrapper for foodstuffs



Patented May 2, i939 irEo F Fl C E WRAPPER FOR FOODSTUFFS Vania NoDrawing. Application September 29, 1932,

' Serial No. 635,402

10 Claims.

The invention relates to wrappers for foodstuifs and particularly tocoated aluminum foil wrappers for butters and cheeses.

Metallic foils have been used quite generally in the packaging of manyarticles and substances, and because of its strength, lightness, goodappearance and other desirable characteristics aluminum foil has beenaccorded preference in many wrapping applications. It has beenrecognized, however, that aluminum foil is not always satisfactory forthe wrapping of certain foodstufis because of the aluminum-corrodingingredients which they contain, such as sodium chloride in the presenceof moisture, and lactic acids. This is particularly manifest in thepackaging of butters and cheeses, where for general use bare aluminumfoil, even in its higher states of commercial purity, cannot beconsidered satisfactory. Although aluminum foil of the usual commercialstandard of purity has proved satisfactory as a wrapper for some of themilder soft cheeses, it invariably fails when used in contact with hardblended cheeses or when exposed for a long period of time to a butter ofhigh salt content.

Various means have been adopted in an attempt to protect the foilwrapper from the aluminum-corroding ingredients in butters and cheeses,but they have met with only indiiferent success. Paper liners of varioussorts with and without protective coatings have been given a thoroughtrial and have proved undesirable forvarious reasons, among which may bementioned the tendency of paper to absorb moisture from the product andassume a pulp-like consistency, making the wrapper unsightly whenremoved and aifording little or no protection to the foil. Moreover, thepaper has some effect as a dialyzing membrane, and instead ofprotecting, it actually hastens corrosion of the foil. Again, paper orother treated cellulosic material is not desirable in contact withfoodstuffs because of its tendency to impart a foreign taste or odorwhich is particularly objectionable in a wrapper for butters. varnishesand lacquers have been tested as protective coatings for the foil,including'both natural and synthetic resins, but these also have failedto satisfactorily solve the problem of providing a coating whichwill notonly protect the food product from'outside odors, but which will' notitself impart an odor and which will preserve the product for therequisite length of time.

I have found that if the aluminum foil wrapper is provided with acoating prepared from synthetic resins containing as a principalingredient polymerized vinyl' esters, the difficulties inherent inwrappers heretofore known and used will be largely overcome. I havefound further that the preservative life of aluminum foil provided withthis particular type of coating is much reater than that of aluminumfoil coated with ordinary lacquers or varnishes. The vinyl estercoatings possess the further advantage of reducing the tendency of thewrapper to stick to the butter or other foodstuffs, so that it can beremoved without leaving unsightly lumps of food adhering to the wrapper.

The esters which I have found to be best suited as coatings for foilbutter and cheese wrappers are vinyl acetate and vinyl chloride, or aresin containing both vinyl acetate and vinyl chloride. These esters, intheir polymerized or associated forms, are combined with a suitablesolvent and, if desired, a small quantity of a plasticizer such asdibutyl phthalate is added.

The acetate and the chloride when used in combination may be blended inany desired proportions and the advantages of my invention will berealized to an appreciable extent irrespective of the particularratio-chosen. Furthermore, it will be understood that while the termsvinyl chloride and vinyl acetate are frequently employed throughout thespecification, reference to i the mono-molecular form of these compoundsis not intended per se, but since they are believed to be polymerized,it is the polymerized or associated forms which are indicated in the useof these terms.

As an example by which those skilled in the art may be enabled toreadily practice the invention, I have found that a synthetic resinconsisting of '80 parts vinyl chloride'and 20 parts vinyl acetate giveshighly satisfactory results for the purpose of the invention whenutilized in the manner now to be described.

To a solution of the polymerized vinyl compound in .acetone is added aplasticizer such as dibutyl phthalate and a solvent. A 37 .5 per centsolution of the vinyl compound may constitute about 40 per cent byweight of the mixture; dibutyl phthalate about 3 per cent by weight; andthe solvent about 57 per cent by weight. A satisfactory solvent consistsof about 50 per cent by volume of ethylene dichloride and about 50 percent by volume of the mono-ethyl ether of ethylene glycol. To this mayalso be added, if desired, a resin, such as para-coumarone resin, toimprove adhesion of the coating to aluminum foil. The coating is brushedor sprayed onto the surface of the foil and allowed to dry in the formof a thin, almost colorless, transparent film, possessing thecharacteristics oftoughness, flexibility and effective resistance toattack by salt water and other aluminum-corroding ingredients of buttersand cheeses for considerable periods of time.

Butter wrapped in aluminum foil provided with a coating of the type andcomposition disclosed hereinabove was found to be in first classpalatable condition at the end of sixteen weeks. Processed cheese,provided with this type of coated wrapper, has been preserved forperiods ranging up to six months, and at the end of this period of timethe cheese was still in excellent condition.

For dibutyl phthalate may be substituted other plasticizers such as dianyl phthalate and tricresyl-phosphate. For the solvent disclosedhereinabove may be substituted such solvents as xylene, toluene, ethylacetate or butyl acetate. The essential feature of the invention is theprovision of an aluminum foil wrapper having a coating of syntheticresins containing as a principal ingredient polymerized vinyl esterswith the addition of suitable plasticizers where required, and appliedto the foil with the use of a suitable solvent.'

A modification of the coatings hereinbefore described which I have foundparticularly useful in many applications of the present invention may bemade by mixing the polymerized vinyl compounds with a nitrocelluloselacquer. An ex- 7 ample of this type of resinous coating is one whichconsists of about 32 per cent by weight of a 35 per cent solution of thevinyl compound in tolu, ene, 5 per cent by weight of wet nitrocelluloseof suitable viscosity, preferably of a Saybolt viscosity of 0.5 secondsto 18 seconds, 3 per cent by weight of dibutyl acetate, and about 60 percent by weight of a solvent such as one having a volume composition ofper centtoluene, 40 percent ethyl acetate and 10 per cent butyl acetate.Larger quantities of nitrocellulose lacquer may be used but I considerthat coatings containing the vinyl compounds in higher ratios to thenitrocellulose lacquer ofl'er somewhat better protecticn to the aluminumfoil. As before, the polymerized vinyl compounds may consist of vinylchloride, vinyl acetate, or a mixture of the two.

, It will be understood that while it is preferred to apply the vinyl'ester coating to the inside of the wrapper, it may, if desired, beapplied to the exterior as well. The coating strengthens the foiland inmany cases produces a wrapper which is sumciently strong to make itunnecessary to use cartons. The coated wrapper is both nonporous andopaque and serves to keep the food product fresh during storage andshipment for longer periods of time than do the ordinary paper wrappers,by cutting down evaporation loss and oxidation.

While I have disclosed specific coating compositions in order to enablethose skilled in the art to successfully practice my invention, itshould beunderstood that variations may be made in the compositionwithout sacrificing the desirable lined in the appended claims.

I claim:

1. As a wrapper for foodstuffs which contain characteristics of theimproved wrapper as dealuminum-corroding ingredients, aluminum foilprovided with a coating rendering said aluminum foil resistant tosaidaluminum-corroding ingredients in the foodstuffs, said coatingconsisting principally of a polymerized vinyl .ester and containing aplasticizer.

2. A wrapperi'or foodstuffs which contain aluminum-corrodingingredients, comprising aluminum foil provided on at least one surfacewith a coating of polymerized vinyl ester, said coating rendering thealuminum foil resistant to aluminum-corroding ingredients in the saidfoodstufls.

3. A wrapper for butters and cheeses containing aluminum-corrodingingredients, comprising a sheet of aluminum foil having on at least onesurface a coating consisting principally of, a polymerization product ofvinyl chloride and vinyl ant to the aluminum-corroding ingredients offoodstuii's enclosed in the wrapper.

5. The method of rendering an aluminum foil wrapper for foodstuflscontaining aluminumcorroding ingredients resistant to attack by saidingredients, which comprises providing the wrap per on at least onesurface with a thin, transparent coating containing a polymerized vinylcompound as a principal ingredient, said coating being applied tothefoil in the form of a solution.

6. As a wrapper for foodstuffs which contain aluminum-corrodingingredients, aluminum foil provided with a coating rendering saidaluminum foil resistant to said aluminum-corroding ingredients in thefoodstuffs, said coating consisting principally of a polymerized vinylresin containing vinyl chloride and vinyl acetate, and containing aplasticizer.

7. A wrapper for foodstuffs containing aluminum-corroding ingredients,comprising aluminum foil provided with a coating consisting principallyof polymerized vinyl esters, a lesser quantity of nitrocelluloselacquer, and a plasticizer, said coating rendering the aluminum foilresistant to the aluminum-corroding ingredients of the foodstuffsenclosed in the wrapper.

8. The method of rendering an aluminum foil wrapper for foodstufiscontaining aluminumcorrodlng ingredients resistant to attack by saidingredients, which comprises providing the wrapper on at least onesurface with a thin, transparent coating containing a polymerized vinylcompound as a principal ingredient, said coating being applied in theform of a solution containing polymerized vinyl ester, a solventtherefor, and a plasticizer.

9. The method of rendering an aluminum foil parent coating containingapolymerized vinyl compound as a principal ingredient, said coating beingapplied in the form of a solution containing polymerized vinyl ester, asolvent'therefor, and a resin which improves the adhesion of the coatingto the foil. I

10. The method of rendering an aluminum foil wrapper for foodstufls'containing aluminumcorroding ingredients resistant to attack by saidingredients, which comprises providing the wrapper on at least onesurface with a thin, transparent coating containing a polymerized vinylcompound as a principal ingredient, said coating being applied in theform of a solution containing polymerized vinyl ester, a solventtherefor, and a lesser quantity of a nitrocellulose lacquer.

' THOMAS MORLEY HILL.

